1. Field of the Invention
The present invention generally relates to techniques for reducing the incidence of urinary tract infections in patients with indwelling catheters, and more particularly to a method of using a weak acidic solution to treat a catheter drainage bag for reducing the incidence of such infections.
2. Description of the Related Art
Research data suggest that indwelling urethral catheters are the management techniques of choice for intractable urinary incontinence or chronic bladder outlet obstruction. The literature indicates that persistent, irreversible urinary incontinence may affect an estimated 50% of patients in tertiary care settings. However, patients who have an indwelling urinary catheter show a high incidence of urinary tract infections as demonstrated by numerous research studies. The catheterized urinary tract has been demonstrated to account for most nosocomial urinary tract infections with resulting bacteriuria. Complications of bacteriuria include obstructed catheters, acute pyelonephritis, bacteremia, periurethral purulent infections, vesicourethral reflux, chronic tubulointerstitial nephritis, chronic renal failure, and death. In addition, systemic symptoms of bacteriuria include fever above 38.4° C., nausea, vomiting, and costovertebral angle tenderness, as well as catheter-related hypovolemic sepsis. The literature supports nontreatment for asymptomatic bacteriuria. Long-term urethral catheterization has been linked with symptomatic bacteriuria (e.g., fever, costovertebral angle, or suprapubic tenderness). Notwithstanding, long-term urethral catheter-associated bacteriuria is said to be the most common nosocomial infection in secondary and tertiary care settings, as well as in home health care environments.
Research studies have indicated that about 40% of all nosocomial infections in the United States are associated with the urinary tract, of which 75% are related directly to indwelling catheterization. Bacteriuria has been demonstrated as a universal consequence of long-term urethral catheterization, where the majority of urinary tract infections occur through microbial ascension from the distal urethral tubule into the bladder cavity. The bladder normally resists infection by two known mechanisms: (1) mechanical factors (i.e., residual urine and the bladder urine volume) and (2) intrinsic factors (i.e., the antibacterial property of the bladder mucosa, urea concentration, osmolarity, and pH, as well as antimicrobial drugs). Factors that contribute to urinary tract infections include structural defects, systemic disorders, sexually transmitted diseases, insertion of a urethral catheter, and long-term indwelling catheterization. Urethral catheterization obliterates the natural cleansing of the urinary mucosa, encouraging the migration of pathogens into the bladder.
Antibiotic-resistant microorganisms are prevalent in long-term care facilities, and long-term indwelling catheters are convenient for transmission of antibiotic-resistant bacterial flora such as (in descending order of frequency) Providencia stuartii, Proteus mirabilis, Morganella morganii, Group D Streptococcus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Entrococcus, and Entrobacter. Moreover, research studies have found that antiseptic bladder irrigation did not prevent bacteriuria in patients with long-term catheters but, rather, promoted antibiotic-resistant microorganisms. Accordingly, routine antiseptic bladder irrigation was not recommended for patients with long-term indwelling catheters. Instead, patient education with regard to long-term catheterization has been recommended as an effective measure in reducing the incidence of catheter-related bacteriuria. However, education of patients by medical personnel appears to be inconsistent and not comprehensive, especially in the case of the elderly.
The available literature contains numerous reports with regard to decontamination of urinary drainage bags. However, the literature is unclear with respect to specific decontamination protocol in the acute or tertiary care setting. Various research reports indicated that following urinary bag decontamination, the incidence of bacteriuria continued. For example, Maizels and Schaeffer report in “Decreased Incidence of Bacteriuria Associated with Periodic Instillation of Hydrogen Peroxide into the Urethral Catheter Drainage Bag,” J. Urol. 123:841-845 (1980), that in a randomized study of thirty-one acute spinal cord injury patients (analyzed according to the log rank and chi-square test) that bacterial contamination of the drainage bag could be eliminated effectively by instilling 30 ml of hydrogen peroxide every eight hours, with measurable cost savings to the patient and to the restorative care environment. Similarly, Holliman et al., “Controlled Trial of Chemical Disinfection of Urinary Drainage Bage”, J. Urol. 60:419-422 (1987), reports a randomized study of fifty-seven patients, in which statistical analysis by t or chi-square test found a significant reduction (P<0.05) in catheter-associated urinary tract infections using 30 ml of hydrogen peroxide in drainage bags every eight hours. However, bacteria continued to be isolated from five of thirty bags. Notwithstanding, Sweet et al., “Evaluation of H2O2 Prophylaxis of Bacteriuria in Patients with Long-Term Indwelling Foley Catheters: A Randomized Controlled Study,” Infect Control 6:263-266 (1985), suggested in a randomized study (N=238) tested by chi-square analysis, that instillation of H2O2 may cause a reduction of nosocomial urinary pathogens but no reduction in the rate of bacteriuria (i.e., the rate of bag contamination in the control group was 34% compared to 17% in the peroxide group, P≦0.05).
In a randomized study reported by Muncie et al., “Once-Daily Irrigation of Long-Term Urethral Catheters with Normal Saline,” Arch. Intern. Med. 68:441-443 (1989), involving thirty-two long-term catheterized patients, routine, once-daily 30 ml normal saline irrigation, analyzed using the paired t test, showed no reduction of catheter obstructions or fevers. Meticulous daily perineal cleaning with soap and water and weekly drainage bag change by specially trained nursing personnel also did not decrease the incidence of urinary bag contamination.
Dille et al., “Increasing the Wearing Time of Vinyl Urinary Drainage Bags by Decontamination with Bleach,” Arch Phys. Med. Rehabil. 74:431-437 (1993), in a randomized study of a two-group parallel design with a pretest and multiple post tests (N=54), analyzed by analysis of covariance and multiple analyses of covariance, showed that daily instillation of 15 ml of 5.25% sodium hypochlorite (household bleach) into urinary drainage bags and rinsed with 150 ml of tap water significantly reduced bacterial growth (0 to 100 colony-forming units (CFU's) per ml). Similar findings were reported by Dille and Kirchhoff, “Decontamination of Vinyl Urinary Drainage Bags by Decontamination with Bleach,” Rehabil. Nurs. 18:292-295 (1993), in a randomized study of fifty-four rehabilitation patients with neurogenic bladder dysfunction who required long-term catheterization. Dille and Kirchhoff found that daily decontamination of drainage bags with dilute bleach (5.25% sodium hypochlorite) demonstrated a 76.5% decrease in urinary bag bacterial growth (no bag cultures were greater than 50 CFU's/ml). However, bleach is a toxic agent, and incidental contact may cause skin irritation, clothing stains, metal corrosion, and harmful fumes if mixed with other disinfectants. Also, sodium hypochlorite is unstable and will dissipate when exposed to light if not used correctly.
In summary, the use of an indwelling catheter has been frequently associated with acute bacteriuria, regardless of strict adherence to urinary catheter care guidelines. The use of antibiotic bladder irrigation has been found to reduce the incidence of infection, but also shown to lead to the emergence of resistant organisms. Finally, while numerous researchers have attempted to reduce bacterial colonization within the collection bag by the instillation of various solutions, no researched agent or method has been shown to be effective in reducing the incidence of bacterial propagation within the catheter drainage bag. As such, a need persists for an improved method to reduce the incidence of urinary tract infections in patients with indwelling catheters.